Analysis of pits induced stresses due to metal corrosion

The corrosion damage due to pitting is commonly observed in a wide range of aluminum alloys and structural steels that are being used for aerospace and naval structural applications. In order to predict the nucleation of cracks resulting from nucleation and growth of pits, there is a need to obtain the stress environment around pits. The objective of this study is to investigate the pits induced stresses responsible for possible crack nucleation using the photomicrographs of corroded aluminum 5059 alloy samples using stress analysis. An analysis procedure is developed using CAD and finite element analysis to predict stresses due to single and/or multiple corroded pits. The analysis was performed to investigate stress distributions on the corrosion surface as a function of sensitization time. The results obtained indicate that as the duration of the specimen sensitization increased from 50 days to 74 days, the highest stress levels have increased by about 56%. However, further increase in the sensitization time from 74 to 100 days has very little effect on the stress level. The observed severe exfoliation or the tearing of the sample surface layers in and around the pits is due to the nucleation and coalescence of fine cracks. The cracks are nucleated because of the production and the buildup of differential stresses along the sample thickness.